Experimental diagenesis of organo-mineral structures formed by microaerophilic Fe(II)-oxidizing bacteria.

Experimental diagenesis of organo-mineral structures formed by microaerophilic Fe(II)-oxidizing bacteria.

Nature communications (2015-02-19)

Aude Picard, Andreas Kappler, Gregor Schmid, Luca Quaroni, Martin Obst

ABSTRACT

Twisted stalks are organo-mineral structures produced by some microaerophilic Fe(II)-oxidizing bacteria at O2 concentrations as low as 3 μM. The presence of these structures in rocks having experienced a diagenetic history could indicate microbial Fe(II)-oxidizing activity as well as localized abundance of oxygen at the time of sediment deposition. Here we use spectroscopy and analytical microscopy to evaluate if--and what kind of--transformations occur in twisted stalks through experimental diagenesis. Unique mineral textures appear on stalks as temperature and pressure conditions increase. Haematite and magnetite form from ferrihydrite at 170 °C-120 MPa. Yet the twisted morphology of the stalks, and the organic matrix, mainly composed of long-chain saturated aliphatic compounds, are preserved at 250 °C-140 MPa. Our results suggest that iron minerals might play a role in maintaining the structural and chemical integrity of stalks under diagenetic conditions and provide spectroscopic signatures for the search of ancient life in the rock record.

MATERIALS

Product Number

Brand

Product Description

71063

Sigma-Aldrich

Goethite, 30-63% Fe

700320

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 5 nm avg. part. size, 5 mg/mL in toluene

700304

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 20 nm avg. part. size, 5 mg/mL in toluene

700312

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 10 nm avg. part. size, 5 mg/mL in toluene

310069

Sigma-Aldrich

Iron(II,III) oxide, powder, <5 μm, 95%

725366

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 20 nm avg. part. size, 5 mg/mL in H₂O

725358

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 10 nm avg. part. size, 5 mg/mL in H₂O

725331

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 5 nm avg. part. size, 5 mg/mL in H₂O

518158

Sigma-Aldrich

Iron(II,III) oxide, 99.99% trace metals basis

790508

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 5 nm avg. part. size (TEM), PEG functionalized, 1 mg/mL Fe in H₂O, dispersion

747254

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 10 nm avg. part. size (TEM), carboxylic acid functionalized, 5 mg/mL Fe in H₂O, dispersion

747300

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 10 nm avg. part. size (TEM), amine functionalized, 1 mg/mL Fe in H₂O, dispersion

747408

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 30 nm avg. part. size (TEM), PEG functionalized, 1 mg/mL Fe in H₂O, dispersion

637106

Sigma-Aldrich

Iron(II,III) oxide, nanopowder, 50-100 nm particle size (SEM), 97% trace metals basis

747319

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 10 nm avg. part. size (TEM), PEG functionalized, 1 mg/mL Fe in H₂O, dispersion

747343

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 5 nm avg. part. size (TEM), amine functionalized, 1 mg/mL Fe in H₂O, dispersion

747327

Sigma-Aldrich

Iron oxide(II,III), magnetic nanoparticles solution, 30 nm avg. part. size (TEM), amine functionalized, 1 mg/mL Fe in H₂O, dispersion